Magnetocaloric effects of 2D adsorbed O₂

Physisorbed 2D O 2 shows saturation magnetisation even within magnetic fields whose magnetic energy mu .B is small compared with the thermal energy of the molecules k*T. This is demonstrated by detection of large magnetocaloric effects, which are for the first time reported for a 2D magnetic systems. The saturation magnetisation at low fields proves that Bloch's spin-wave theory for two dimensions is applicable to 2D physisorbed O 2 and gives evidence for the relevance of this theory from a system which is in a much more ideal manner an approximation to 2D than the evaporated magnetic films studied up to now. In analogy to Koringa's work about nuclear-spin-lattice relaxation in the framework of nuclear magnetic cooling the authors call the observed spin-lattice non-equilibrium phenomenon the '2D Korringa effect'.